Vaccination is one of the most effective methods for preventing infectious diseases. However, a single administration of an antigen is often not sufficient to confer optimal immunity and/or a long-lasting response. Approaches for establishing strong and lasting immunity to specific pathogens include addition of adjuvants to vaccines and/or repeated vaccination, i.e. boosting an immune response by administration of one or more further doses of antigen. Such further administrations may be performed with the same vaccine (homologous boosting) or with a different vaccine (heterologous boosting). The most common approach for homologous boosting is not only to administer the same vaccine, but also to administer it in the same dose as the earlier administration.
Tuberculosis (TB) is a chronic infectious disease caused by infection with Mycobacterium tuberculosis and other Mycobacterium species. It is a major disease in developing countries, as well as an increasing problem in developed areas of the world.
The protein antigens Mtb72f and M72 (described, for example, in international patent applications WO2006/117240 and WO2012/080369 which are incorporated herein by reference) or fragments or derivatives thereof are protein antigens of potential benefit for the treatment or prevention of tuberculosis. Previous investigations have led to M72 being administered in humans in conjunction with the immunostimulants 3-O-deacylated monophosphoryl lipid A (3D-MPL) and QS21 in a liposomal formulation and in a 0,1 month schedule using 10 ug M72, 25 ug 3D-MPL and 25 ug QS21 (Leroux-Roels et al Vaccine 2013 31 2196-2206, Montoya et al J. Clin. Immunol. 2013 33(8): 1360-1375).
A candidate vaccine utilising the antigen M72 is currently in a Phase IIB trial (ClinicalTrials.gov Identifier: NCT01755598) to evaluate the protective efficacy of two doses against pulmonary TB, as compared to placebo, in adults aged 18-50 living in TB endemic countries.
There remains a need for novel methods of immunising against diseases, including tuberculosis, which are highly efficacious, safe, cost-effective, long-lasting and induce a broad spectrum of cross-reactive immune responses.